Immunostimulatory properties of human dendritic cells generated using IFN-beta associated either with IL-3 or GM-CSF.

Despite limited clinical efficacy in large trials, dendritic cells (DC)-based immunization has yielded impressive responses in some patients. Key questions remain to be solved in order to optimize this therapeutic vaccine. Among them, the nature of the DC type used and its state of maturation are pivotal. Besides myeloid DC which are mostly used in clinical trials, a new DC type has been recently described resulting from the differentiation of monocytes in the presence of type I IFNs. In the present study, we analyze the features of type I IFNs DC generated in the presence of either IL-3 (IL-3-DC) or GM-CSF (GM-CSF-DC) and compare their capacity to respond to poly(I:C) and to subsequently trigger T-cell activation. The two DC types disclose a similar immunophenotype characterized by high levels of chemokines receptors, co-stimulatory and HLA molecules expression. After poly(I:C) maturation, both DC types display a marked upregulation of CD80, CD83 and CD86 and the same pattern of gene expression. In addition, poly(I:C) stimulated them to secrete IFN-alpha and IL-12p70. Both DC types elicit potent allogeneic reactions. Priming of autologous T cells by IL-3-DC or GM-CSF-DC pulsed with an HLA-A2 restricted melan-A derived peptide, lead to the expansion of peptide specific CTL secreting high amounts of IFN-gamma. We conclude that poly(I:C) matured IL-3-DC and GM-CSF-DC share similar phenotype and functional properties including the capacity to prime tumor-associated antigen specific CTL.

Interleukin-3 and interferon beta cooperate to induce differentiation of monocytes into dendritic cells with potent helper T-cell stimulatory properties.

It was observed that interferon beta (IFN-beta) prevents the down-regulation of the interleukin-3 receptor alpha chain (IL-3Ralpha), which spontaneously occurs during culture of human monocytes. The functionality of IL-3R was demonstrated by the fact that IL-3 rescued IFN-beta-treated monocytes from apoptosis. Monocytes cultured in the presence of IFN-beta and IL-3 acquire a dendritic morphology and express high levels of HLA antigen class I and class II and costimulatory molecules. When stimulated by either lipopolysaccharide or fibroblasts expressing CD40 ligand (CD40L) transfectants, dendritic cells (DCs) generated in IFN-beta and IL-3 secreted high levels of IL-6, IL-8, and tumor necrosis factor-alpha but low levels of IL-12 in comparison with DCs generated in IL-4 and granulocyte-macrophage colony-stimulating factor (GM-CSF). In mixed leukocyte culture, IL-3-IFN-beta DCs induced a vigorous proliferative response of allogeneic cord blood T cells and elicited the production of high levels of IFN-gamma and IL-5 by naive adult CD4+ T cells. Finally, IL-3-IFN-beta DCs were found to produce much higher levels of IFN-alpha than IL-4-GM-CSF DCs in response to Poly (I:C) but not to influenza virus. It was concluded that monocytes cultured in the presence of IL-3 and IFN-beta differentiate into DCs with potent helper T-cell stimulatory capacity despite their low secretion of IL-12.